1. CCT203 – Chapter 10
ETHERNET CONCEPTS

2. Topics
• LANs AND WANs
• Internet and Intranet
• Ethernet / Fast Ethernet / Token Ring
• Protocols
• Media
• Topologies
• Collisions
• Transceivers
• Network Interface Cards
• Hubs / Repeaters

3. LANs (Local Area Networks)
• A network is any collection of
independent computers that
communicate with one another over
a shared network medium.
• LANs are networks usually confined
to a geographic area, such as a
single building or a college campus.

4. LANs (Local Area Networks)
• LANs can be small, linking as few as three
computers, but often link hundreds of
computers used by thousands of people.
• The development of standard networking
protocols and media has resulted in
worldwide proliferation of LANs throughout
business and educational organizations.

5. WANs (Wide Area Networks)
• Wide area networking combines
multiple LANs that are geographically
separate.
• This is accomplished by connecting the
different LANs using services such as;
– Dedicated leased phone lines
– Dial-up phone lines (both synchronous and
asynchronous)
– Satellite links and
– Data packet carrier services.

6. WANs (Wide Area Networks)
• Can be as simple as a modem and remote
access server for employees to dial into
the network.
• Or it can be as complex as hundreds of
branch offices globally linked using special
routing protocols.

7. INTERNET
• The Internet is a system of linked
networks that are worldwide in scope
and facilitate data communication
services such as;
– Remote login
– File transfer
– Electronic mail
– The World Wide Web and
– Newsgroups

8. INTERNET
• The Internet was initially restricted to
military and academic institutions.
• But now it is a full-fledged conduit for any
and all forms of information and
commerce.
• Internet websites now provide personal,
educational, political and economic
resources to every corner of the planet.

9. INTRANET
• An intranet is a private network
utilizing Internet-type tools, but
available only within that organization.
• For large organizations, an intranet
provides an easy access mode to
corporate information for employees.

10. ETHERNET
• Ethernet is the most popular physical
layer LAN technology in use today.
• Other LAN types include
– Token Ring, Fast Ethernet
– Fiber Distributed Data Interface (FDDI)
– Asynchronous Transfer Mode (ATM) and
– LocalTalk.

11. ETHERNET
• Ethernet is popular because it strikes a
good balance between speed, cost and
ease of installation.
• The Institute for Electrical and Electronic
Engineers (IEEE) defines the Ethernet
standard as IEEE Standard 802.3.
• By adhering to the IEEE standard, network
equipment and network protocols can
communicate efficiently.

12. FAST ETHERNET
• For Ethernet networks that need
higher transmission speeds, the Fast
Ethernet standard (IEEE 802.3u) has
been established.
• This standard raises the Ethernet
speed limit from 10 Megabits per
second (Mbps) to 100 Mbps.

13. FAST ETHERNET
• There are three types of Fast Ethernet:
– 100BASE-TX for use with level 5 UTP cable
– 100BASE-FX for use with fiber-optic cable and
– 100BASE-T4 which utilizes an extra two wires for use with
level 3 UTP cable.
• Gigabit Ethernet is a future technology
that promises a migration path beyond
Fast Ethernet that support even higher
data transfer speeds.

14. TOKEN RING
• Token Ring is another form of
network configuration in which all
messages are transferred in a
unidirectional manner along the ring
at all times.
• Data is transmitted in tokens, which
are passed along the ring and
viewed by each device.

15. TOKEN RING
• When a device sees a message
addressed to it, that device copies the
message and then marks that message as
being read.
• Eventually message gets back to the
sender who now notes that the message
was received by the intended device.
• The sender can then remove the message
and free that token for use by others.

16. PROTOCOLS
• Network protocols are standards that
allow computers to communicate.
• A protocol defines;
– How computers identify one another on a
network
– The form that the data should take in transit
– How information is processed once it reaches its
final destination and
– Procedures for handling lost or damaged
transmissions or "packets.“

17. PROTOCOLS
• The main types of network protocols
in use today include;
– TCP/IP (for UNIX, Windows NT, Windows
95 and other platforms)
– IPX (for Novell NetWare)
– DECnet (for networking Digital Equipment
Corp. computers)
– AppleTalk (for Macintosh computers) and
– NetBIOS/NetBEUI (for LAN Manager and
Windows NT networks)

18. PROTOCOLS
• Although each network protocol is
different, they all share the same physical
cabling.
• This concept is known as "protocol
independence"

19. MEDIA
• There are four major types of media
in use today:
– Thick wire for 10BASE5 networks
– Thin coax for 10BASE2 networks
– Unshielded twisted pair (UTP) for 10BASE-T
networks and
– Fiber optic for 10BASE-FL or Fiber-Optic Inter-
Repeater Link (FOIRL) networks.
• The most popular wiring schemes
are 10BASE-T and 100BASE-TX,
which use unshielded twisted pair
(UTP) cable.

20. MEDIA
• Level 5 cable is the highest, most
expensive grade, offering support for
transmission rates of up to 100 Mbps.
• Level 4 and level 3 cable are less
expensive, but cannot support the same
data throughput speeds.
• Level 4 cable can support speeds of up to
20 Mbps; level 3 up to 16 Mbps.

21. MEDIA
• For specialized applications, fiber-
optic, or 10BASE-FL, Ethernet
segments are popular.
• Fiber-optic cable is more expensive,
but it is invaluable for situations
where electronic emissions and
environmental hazards are a
concern.

22. MEDIA
• Fiber-optic cable is often used in
interbuilding applications to insulate
networking equipment from electrical
damage caused by lightning.
• The Ethernet standard allows for fiber-
optic cable segments up to 2 kilometers
long.

23. TOPOLOGIES
• A network topology is the geometric
arrangement of nodes and cable
links in a LAN.
• Used in two general configurations:
– Bus and Star

24. TOPOLOGIES
• Topologies define how nodes are
connected to one another.
• A node is an active device connected to
the network, such as a computer or a
printer.
• A node can also be a piece of networking
equipment such as a hub, switch or a
router.

25. BUS TOPOLOGY
• A bus topology consists of nodes
linked together in a series with each
node connected to a long cable or
bus.
• Many nodes can tap into the bus and
begin communication with all other
nodes on that cable segment.

26. BUS TOPOLOGY
• A break anywhere in the cable will usually
cause the entire segment to be inoperable
until the break is repaired.
• Examples of bus topology include
10BASE2 and 10BASE5.

27. STAR TOPOLOGY
• 10BASE-T Ethernet and Fast
Ethernet use a star topology.
• Access is controlled by a central
computer.
• Generally a computer is located at
one end of the segment, and the
other end is terminated in central
location with a hub.

28. STAR TOPOLOGY
• The central location can be a telephone closet or
other area where it is convenient to connect the
UTP segment to a backbone.
• The primary advantage of this type of network is
reliability, for if one of these 'point-to-point'
segments has a break, it will only affect the two
nodes on that link.
• Other computer users on the network continue
to operate as if that segment were nonexistent.

29. COLLISIONS
• Ethernet is a shared media, so there
are rules for sending packets of data
to avoid conflicts and protect data
integrity.
• It is possible that two nodes at
different locations attempt to send
data at the same time.
• When both PCs are transferring a
packet to the network at the same
time, a collision will result.

30. COLLISIONS
• Increased collisions are often the result of too
many users on the network, which results in a lot
of contention for network bandwidth
• Collision can slow the performance of the
network from the user's point of view.
• Segmenting, where a network is divided into
different pieces joined together logically with a
bridge or switch, is one way of reducing an
overcrowded network.

31. TRANSCEIVERS
• Transceivers are used to connect nodes
to the various Ethernet media.
• Most computers and network interface
cards contain a built-in 10BASE-T or
10BASE2 transceiver
• Many Ethernet devices provide an AUI
connector to allow the user to connect to
any media type via an external
transceiver.

32. TRANSCEIVERS
• The AUI connector consists of a 15-pin D-shell
type connector, female on the computer side,
male on the transceiver side.
• Thick wire (10BASE5) cables also use
transceivers to allow connections.
• For Fast Ethernet networks, a new interface
called the MII (Media Independent Interface)
was developed to offer a flexible way to support
100 Mbps connections.
• The MII is a popular way to connect 100BASE-
FX links to copper-based Fast Ethernet devices.

33. Network Interface Cards
• Network interface cards, commonly
referred to as NICs, are used to
connect a PC to a network.
• The NIC provides a physical
connection between the networking
cable and the computer's internal
bus.

34. Network Interface Cards
• Many NIC adapters comply with Plug-n-Play
specifications in which, NICs are automatically
configured without user intervention.
• Fast Ethernet NICs are often 10/100 capable,
and will automatically set to the appropriate
speed.
• Full duplex networking is another option, where
a dedicated connection to a switch allows a NIC
to operate at twice the speed.

35. HUBS / REPEATERS
• Hubs/repeaters are used to connect
together two or more Ethernet segments
of any media type.
• Signal quality begins to deteriorate as
segments exceed their maximum length.
• Hubs provide the signal amplification
required to allow a segment to be
extended a greater distance.

36. HUBS / REPEATERS
• A hub takes any incoming signal and
repeats it out all ports.
• Ethernet hubs are necessary in star
topologies such as 10BASE-T.
• A network of hubs/repeaters is termed a
"shared Ethernet," meaning that all
members of the network are contending
for transmission of data onto a single
network (collision domain).

37. The End